As suggested by the photo in the beginning of this chapter, consumers can rate new HDTVs. Many Web sites use a five point scale. Although the individual responses are not normal, the central limit result applied to each of the four samples does justify treating the treatment means as if the normal assumption prevailed. The summary statistics of ratings for four of the most popular sets at one Web site are
n1 = 14 1 = 4.50
n2 = 20 2 = 3.60 s = 1.56
n3 = 30 3 = 4.13
n4 = 15 4 = 4.56
Use a = .10 and determine:
(a) t intervals for each of the six differences of means.
(b) The six multiple-f intervals.